Scrap Box crashes server if opened in Creative mode

Crash report: https://pastebin.com/dpLYVj6f

Server software:
git-Paper-223 (MC: 1.14.4)
CS-CoreLib vDEV - 78 (git 199e1b1e)
Slimefun vDEV - 323 (git 57e11265)
SlimeXpansion vDEV - 4 (git 5bf10c2)